The present invention relates to a landing position determining method and device for processing-liquid ejection nozzles, and more particularly, to a method and device for determining landing positions of the processing liquid ejected from processing-liquid ejection nozzles in an inkjet recording apparatus having nozzles that eject colorless and transparent processing liquid for agglomerating colored inks.
Conventionally, when an image is printed on a recording medium in an inkjet recording apparatus, there has been a case in which water resistance of a recorded image is insufficient depending on a type of the recording medium.
In particular, when a color image is recorded, if a large quantity of ink is ejected on a recording medium in an attempt to print a high-density image, feathering may be caused depending on penetration of the ink into the recording medium. On the other hand, if it is attempted to print a high-density image while suppressing the penetration, a blur may be caused among inks of different colors. In both the cases, an image quality in printing a color image is substantially deteriorated.
Therefore, in recent years, in order to improve water resistance of a printed image and obtain a high-quality image (print) in an inkjet recording apparatus, a method of using processing liquid is proposed.
The processing liquid has an action of agglomerating and fixing color materials of colored inks. Therefore, when such processing liquid is used in the inkjet recording apparatus, before the colored inks are deposited on the recording medium, the processing liquid is deposited on the recording medium and the colored inks are deposited on the processing liquid. This makes it possible to prevent feathering and a blur of the colored inks on the recording medium and obtain a high-quality image.
In this case, usually, the processing liquid is deposited over an image recording area (image wise) of the colored inks on the recording medium by an inkjet head.
In ejecting the processing liquid, if there is a nozzle that does not eject the processing liquid among nozzles of the inkjet head, an area on which the processing liquid is not deposited is formed on the recording medium.
Naturally, if the colored inks are deposited on the area on which the processing liquid is not deposited on the recording medium, fixing and agglomeration of the color materials of the colored inks is insufficient. Therefore, desired ink density and a desired dot diameter are not obtained and the image quality is deteriorated.
In particular, when the inkjet head has a line head configuration, if a non-ejecting nozzle is present, the processing liquid is not deposited on an area on a recorded image and an image quality in the area is deteriorated, and hence the area appears like a line (streak) and is extremely conspicuous.
As the processing liquid, colorless and transparent processing liquid is used in order to accurately control color density of a recorded image area on the recording medium. Therefore, although it is extremely difficult to detect whether or not the processing liquid is deposited on the recording medium, it is extremely important in maintaining a quality of a recorded image to detect whether or not the processing liquid is deposited on an area on which the ink is to be deposited (image recording area).
Therefore, conventionally, there is known a technology of detecting the colorless and transparent processing liquid by performing test print prior to formal print.
For example, JP 08-118616 A discloses a method of forming a line formed by depositing a colored ink one on top of processing liquid and a line formed by depositing only the colored ink, comparing densities, hues, blurs, and the like of those lines, and detecting a non-ejecting nozzle using a result of the comparison. JP 08-118616 A also discloses a method of, after depositing processing liquid on a recording medium to form a stepped line, depositing a colored ink (solid deposited) over the entire surface of the recording medium, calculating density, a color, and the like of a line on which the processing liquid and the ink overlap, and detecting a non-ejecting nozzle using the density, the color, and the like.
JP 11-198357 A discloses a method of depositing processing liquid on areas on which two colored inks are deposited adjacent to each other on a recording medium, determining whether or not landing positions of the colored inks and the processing liquid coincide with each other, and adjusting the landing position of the processing liquid.
JP 2001-138494 A discloses a method of performing print-alignment for processing liquid and an ink using an optical characteristic that changes according to density and a blur that relatively change.
However, in the method disclosed in JP 08-118616 A, although a nozzle that is not ejecting the processing liquid can be detected, a method of determining a landing position of the processing liquid such that landing positions of the processing liquid and the ink coincide with each other is not disclosed, and hence it is impossible to prevent deterioration in an image quality of a recorded image due to ink fixing failure caused by the shift of the landing positions of the processing liquid and the ink.
In the method disclosed in JP 11-198357 A, the landing position of the processing liquid can be adjusted by adjusting timing of ejection in movement in a scanning direction of processing-liquid ejection nozzles. However, the method can be applied to only an apparatus in which processing-liquid ejection nozzles (processing liquid head) eject the processing liquid while moving in the scanning direction. In other words, the method cannot be applied to an apparatus in which processing-liquid ejection nozzles arranged in parallel in the scanning direction of the processing liquid head are moved in a direction orthogonal to the scanning direction of the processing liquid head to deposit the processing liquid on a recording medium.
In the method disclosed in JP 2001-138494 A, the print-alignment for the processing liquid and the ink can be performed. However, in order to calculate the optical characteristic of the density and the blur of the ink used for aligning printing (recording) of the ink and printing (recording) of the processing liquid, a plurality of patterns formed by depositing the processing liquid on or near a print pattern formed by two kinds of colored inks have to be generated. Therefore, the method is time consuming and there is concern about an individual difference of each of the colored inks.